Vascular/venous access devices for introducing catheters into a patient's vascular system are well known. The simplest of such devices comprises a through-the-needle catheter having a cannula which generally comprises a metal needle inserted into the patient's vein and through which a catheter may subsequently be introduced. A common problem associated with the use of such prior art through-the-needle catheter systems arises in removing the cannula after the catheter has been introduced into the vein. Since the cannula is typically comprised of a rigid metal needle, it is desirable to remove the cannula from the patient's vein after insertion of the catheter to prevent trauma to the vein caused by the cannula's rigid structure and/or sharp tip. However, once the catheter has been inserted into the vein, the cannula can typically only be removed by retracting the same upwardly along the catheter, thereby exposing the patient as well as administering personnel to accidental contact with the cannula.
In recognizing the discomfort and extraction problems of the cannula associated with through the needle catheter systems, over-the-needle catheter systems have been widely utilized for venous access applications. In such over-the-needle catheter systems, a thin catheter having a hub at its proximal end is placed over a rigid cannula, such as a needle, whereby the cannula as well as the catheter may be simultaneously inserted into the vein of a patient. Once the cannula and catheter and have been introduced into the vein, the cannula may be withdrawn from the interior of the catheter leaving the catheter disposed within the patient's vein. Subsequently, required administration line communication can be effectuated with the catheter by interconnection with its hub mounted to the proximal end of the catheter. However, due to such over-the-needle catheters being inserted into the vein of the patient concurrently with the rigid cannula, such over-the-needle catheters must possess sufficient rigidity to prevent the same from traveling axially upward relative the cannula during the insertion process. As such, such over-the-needle catheters are limited in their axial length and are incapable of being inserted upwardly through the length of the vein or artery without causing trauma and/or puncture to the vein.
In recent years, the desirability of utilizing a peripherally inserted central catheter (PICC) line into a patient for medical applications has become widespread. In such PICC line applications, a flexible catheter must be introduced into the vascular system of a patient and subsequently be manipulated to allow the catheter to wind its way upwardly through the vascular system to a desired location. Due to the requirement of advancing the catheter upwardly through the vascular system, the catheter must be formed from a soft, biocompatible, pliable, and flexible material which is capable of winding through and extending through substantial axial lengths of the vascular system, i.e. from two to thirty inches or more, without causing trauma to the vascular system or puncturing therethrough. In view of such requirements, heretofore, through-the-needle catheter systems have been typically utilized wherein after venous insertion, the cannula is retained within the patient and the desired length of catheter is inserted through the cannula and into the vein of the patient. In such applications, blood leakage is commonplace which exposes administering personnel to substantial health risks, such as that associated with the AIDS virus, hepatitis, and other infectious diseases.
In view of these concerns, recently an over-the-needle catheter system has been introduced specifically adapted for PICC line applications which attempts to minimize accidental exposure of medical personnel to patient's blood. This particular venous access device is manufactured by Menlo Care, Inc. of Palo Alto, California and is marketed under the trademark LANDMARK venous access device.
Additionally, in recognizing the desirability of providing an improved vascular/venous access device which would permit the introduction of an unlimited length of catheter into a patient's vascular system and which facilitates removal of the needle to prevent accidental punctures and/or exposure; which is simple and inexpensive to fabricate; and which requires a minimum of training and manipulative skill to practice, Applicant previously invented an improved vascular/venous access device. The improved vascular/venous access device allows insertion of a flexible over-the-needle catheter of unlimited axial length utilizing a relatively short cannula and facilitates removal of the cannula from the catheter. The improved vascular/venous access device is described in Applicant's U.S. patent application Ser. No. 07/669,679, filed Mar. 4, 1991, now U.S. Pat. No. 5,112,312 entitled VASCULAR/VENOUS ACCESS DEVICE AND METHOD OF UTILIZING AND FORMING THE SAME, the entire disclosure of which is expressly incorporated herein by reference. In this vascular/venous access device the distal or sharp end of a needle cannula extends outwardly from the distal end of the catheter and the proximal end of the needle cannula exits the central bore of the catheter through a hole or slit formed in the side wall a short distance from the distal end of the catheter. A gripping device selectively locks the needle cannula in place within the bore of the catheter and provides a means for gripping the venous access device during insertion of the needle cannula and catheter into a patient's vein, artery, or the like.
The needle cannula provides a rigid and sharp implement for effecting entry into the patient's vascular system. After the needle cannula and catheter have entered the vascular system, the needle cannula is withdrawn from the catheter and the gripping device may be removed or alternatively used as a catheter guide or tape site. The desired length of the catheter may then be manually advanced into the vascular system to a desired position.
The catheter is preferably formed having a generally rigid tip portion disposed along a substantial length of the needle cannula with the remaining length of the catheter being formed having a soft flexible configuration. The rigid portion prevents buckling and/or axial compression of the catheter during the insertion process and subsequently softens upon contact with blood and/or liquids introduced via administration through the catheter or from the thermal gradient caused from patient residence such that a soft flexible tip is then provided for manipulation of the catheter within the vascular system.
The catheter is preferably formed by a sequential mandrel dip process. More particularly, the rigid tip portion may be formed by dipping a mandrel into a solubilized softenable material and allowing the softenable material to dry on the mandrel. The softenable material is preferably hydrated from the mandrel and the desired length for the distal tip portion is cut off. This distal portion is then applied to and dried on a secondary dipping mandrel and a length of flexible catheter is inserted over the mandrel such that the catheter abuts the softenable distal portion. The softenable portion and the portion of flexible catheter are then dipped into a liquid polymer such that the two portions are solvent welded together and an outer layer of polymer is deposited thereover. Thus a contiguous assembly is formed by bonding the softenable material to the distal end of the flexible catheter. The assembly is then allowed to dry and the dipped softenable tip portion is trimmed to exhibit a profile that facilitates insertion into a patient. The mandrel is subsequently removed from the assembly of the catheter and the softenable portion such that a continuous lumen is formed within both portions. A needle cannula is then inserted through the wall of the catheter and extended axially through the length of the catheter such that its sharp tip extends outwardly beyond the softenable end of the catheter.
A flashback chamber is commonly used with vascular/venous access devices, such as that of Applicant's above-described prior invention, to provide an indication that the tip of the needle cannula has entered a vein. Entry of the tip of the needle cannula into a vein is indicated by flashing or blood entering the flashback chamber. The flashback chamber contains the blood, thus reducing health risks and preventing spillage. The flash chamber is attached to and in fluid communication with the needle cannula and may be formed as an integral part thereof.
In the vascular/venous access device of pending U.S. patent application Ser. No. 07/669,679, the needle cannula may be exposed after it is withdrawn from the catheter, thus presenting a possible health risk to administering personnel. In contemporary over-the-needle insertion devices the needle is similarly exposed after being withdrawn for disposal.
In view of the shortcomings of the prior art, it is desirable to provide a needle-safe flashback chamber for use with vascular/venous access devices wherein the needle cannula is automatically captured within a protective sheath upon being withdrawn from the patient to prevent accidental exposure of administering personnel to substantial health risks, such as that associated with the AIDS virus, hepatitis, and other infectious diseases.